Biometrics allows a person to use a unique part of their body for identification purposes.
Many different body part templates have been suggested for biometrics, including fingerprints, face prints, retinal scans and DNA sequences.
Many different ways of obtaining and using biometric information are well known in the art. The body part is compared with a prestored template. A match between the part and the template allows some action to be taken. Effectively these previous biometric systems used the biometric information as a key that opens a lock. The biometric information is compared with a template. The lock opens based on the comparison.
Continuing the analogy, once the key has unlocked the lock, the user has access to information.
Encryption has also been used for security, but in a different way. Encryption is used to change the information itself. No lock and key is necessary—the information can be disseminated, and the decryption key can be used to retrieve it.
Encryption is often used for messages, e.g. by email. Encryption is also used to keep private certain information in an account, for example.
One popular kind of encryption is public key cryptography. The encryption key is public and anyone can use it. Only the person having the private key can decrypt a message, however. If user A encrypts a message with user B's public key, only B can decrypt the message. No one else, not even user A, can decrypt the message. Other similar cryptosystems are known. All have in common that there must be a decryption key  typically a large number.